By Paul J. Sniadecki, MLSA Board Director

European frog-bit, an Aquatic Invasive Species (AIS) probably arrived in North America around 1930.  Nearly a century later, frog-bit has become a significant invasive, especially along parts of Lake Huron and inland lakes/streams in southeast Michigan. The plant forms mats in surface waters so thick that they block sunlight and diminish oxygen levels for native species.  The mats are so thick that many times it is impossible to swim, boat, or fish. Frog-bit also defies effective control.

Frog-bit has been listed for years on Michigan’s Invasive Species Watch List.  That “list” identifies invasive species that pose an immediate or potential threat to the economy, environment, and/or human health. Watch list species have limited known distribution or have never been confirmed in the wild in our state.

The Michigan Invasive Species Program prioritizes watch list species and encourages the public to report potential sightings and take precautions to prevent establishment or limit their spread. Several factors are considered in evaluating species for watch list status, including risk assessments, proximity of populations to Michigan, harmful characteristics and availability of control methods. The Watch List is a joint effort of the departments of Environment, Great Lakes, and Energy (EGLE); Natural Resources (DNR); and Agriculture and Rural Development (MDARD).

Unfortunately, frog-bit has now been de-listed from the Watch List.  A recent review of that invasive aquatic plant, determined that the plant no longer met watch list criteria due to its establishment in many areas of the state. European frog-bit still retains its prohibited status, making it unlawful to possess, introduce, import or sell in Michigan. State and local management control efforts for European frog-bit will continue, as the frog-bit bite is deep.

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